The unofficial close of of summer swimming season, Labor Day weekend, arrives after several popular beach swimming areas logged high levels of bacteria or algae toxins earlier this week.

Four state park beaches and two locally run beaches reported high bacteria levels in samples pulled early this week. They were Clear Lake, Lake Keomah, Pine Lake and Union Grove state park beaches, along with Orleans Beach on Big Spirit Lake and Hickory Grove near Colo.

In addition, Big Creek, Rock Creek and Green Valley state beaches had levels of an algal toxin, microcystin, that exceeded swimming standards.

High bacteria means the presence of organisms that can cause intestinal illness or skin infections. Microcystin can upset stomachs, and, in extreme cases, cause neurological problems. Livestock and pets, such as dogs, are particularly vulnerable to the toxins.

Levels of pathogens and toxins in lakes can vary by the hour. Swimmers should avoid swallowing the water and bathe immediately after swimming, if they decide to use the swimming areas.